Ceiling baffles and reflectors for controlling lecture-room sound for speech intelligibility

Abstract

Reinforcing speech levels and controlling noise and reverberation are the ultimate acoustical goals of lecture-room design to achieve high speech intelligibility. The effects of sound absorption on these factors have opposite consequences for speech intelligibility. Here, novel ceiling baffles and reflectors were evaluated as a sound-control measure, using computer and 1/8-scale models of a lecture room with hard surfaces and excessive reverberation. Parallel ceiling baffles running front to back were investigated. They were expected to absorb reverberation incident on the ceiling from many angles, while leaving speech signals, reflecting from the ceiling to the back of the room, unaffected. Various baffle spacings and absorptions, central and side speaker positions, and receiver positions throughout the room, were considered. Reflective baffles controlled reverberation, with a minimum decrease of sound levels. Absorptive baffles reduced reverberation, but reduced speech levels significantly. Ceiling reflectors, in the form of obstacles of semicircular cross section, suspended below the ceiling, were also tested. These were either 7 m long and in parallel, front-to-back lines, or 0.8 m long and randomly distributed, with flat side up or down, and reflective or absorptive top surfaces. The long reflectors with flat side down and no absorption were somewhat effective; the other configurations were not.

Effects of classroom-acoustic change on the attention level of university students

“…At the same time, it confirms what Escalona (2006) and Yang and Hodgson (2007) pointed, regarding the need to shorten the reverberation time as a control measure of acoustics in the classrooms, in order to improve the intelligibility in those spaces.…”

“…These alterations include classroom-acoustic change and attention InterdIscIplInarIa, 2016, 33, 2, 201-214 architectural changes, using sound-field amplification (Flagg-Williams et al, 2011;Weil, 2011), or ceiling baffles and reflectors (Dockrell & Shield, 2006;Yang & Hodgson, 2007), that allow changing the reverberation levels of sound in order to modify the need teachers have to modulate their voice and avoid wearing it out (Irvine & Richards, 1998;Möser, Zimmermann & Ellis, 2009;Wilson, 2005).…”

On boundary conditions for the diffusion equation in room-acoustic prediction: Theory, simulations, and experiments

“…[18][19][20][21][22] In this study, a 1: sheet of 5 / 4 in. plywood in thickness are used as wall materials to construct the room model.…”

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“…According to Zannin and Zwirtes [5], acoustical comfort in primary and secondary school classrooms, as well as university classrooms, has been the focus of several studies around the world [10][11][12][13][14][15][16][17][18][19]. Another focus of study mentioned by these authors is students' and professors' noise perception, as well as the influence of noise on people [17,[20][21][22].…”